There is a known technique for applying a coating solution to the surface of a backing sheet (web), such as a flexible film, using a die coater. Patent Documents 1 and 2 disclose an example of such a technique, which includes applying a coating solution to a backing sheet using a slot die coater while feeding the backing sheet as a backup roller rotates, wherein the slot die coater is located across the backing sheet from the backup roller.
The backing sheet has first and second surfaces, in which the first surface is to be coated with the coating solution, and the second surface is opposite to the first surface. The backup roller rotates with its outer surface in contact with the second surface of the backing sheet. The slot die coater for discharging the coating solution is placed at a position facing the contact part of the backing sheet in contact with the backup roller. The coating solution is discharged from the slot die coater to the backing sheet being fed by the rotation of the backup roller, so that the first surface of the backing sheet is coated with the coating solution.